Ok, torhu was faster and his explanation is better.

Then I add to this thread by stating that I get the above described Vintage D pedal glitch as well on low audio buffer settings with my Focusrite Saffire interface.
And I can not see this being a problem with system optimization, as I can run the supposedly much more ressourcehungry Ivory II libraries on ridiculously low buffer sizes without any glitches. LatencyMon and DPC Latency Checker do not indicate any problems with my system.
I think the Kontakt Player just doesn't like my system too much, as I have exactly the same problems with Galaxy The Giant.

I want to add that piano glitch ended after I updated to version 1.2 , so if you haven't updated, it's worth a try.
But I also now get some general (non pedal related) cracks and pops, but it's minor.

I'm still interested in that si-bemol (biflat) note's case in 2nd octave (I think its second octave, my "music grammar" not being my strong point) that sounds quieter than other notes. Perhaps it's just my perception of it, but in waveform it also shows quiet.

I already got version 1.2 delivered, so that's not the issue. And as said, it happens on The Giant as well.

By the way, for v1.2. in "global presets" section the list of options is shorter than older version. Why so?

Could somebody please check this for me: Can Vintage D be set to mono playback and does it sound good even in headpohnes (without any distortions or other unpleasant effects)? Thanks you, H.

Yes, it can be set to mono. Although I seldom use headphones it sounds ok when I do. Perhaps someone that uses headphones more will address that.

Thank you.